Throat plates for sewing machines



Nov. 10, 1959 w. G. JOHNSON 2,911,931

THROAT PLATES FOR SEWING MACHINES Filed Oct. 26, 1956' w i f V W V7 25 W Fig.2

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INVENTOR.

Wa/ fer G. Johnson w/T/vEss mm E W United States Patent 2,911,931 THROAT PLATES For: snwnsc; MACHINES Walter G. Johnson, Bridgeport, Conn., assignor to The Singer Manufacturing Company, Elizabeth, N.J., a corporation of New Jersey Application October 26, 1956, SerialNol 618,604

2 Claims. (Cl. 112-460) Patented Nov. 10, 1959 2 rubberlike cushioning material in an arrangement highly effective to danipen noise and vibration commensurate with a high degree of stability in the support thereof. b

The above and other objects and advantages of this invention will appear from the following description hav ing reference to the accompanying drawings in which:

Fig. 1 represents an end elevational view, partly in section, of a portion of a sewing machine having applied thereto a throat plate embodying my invention and including portions of the sewing machine needle bar and presser mechanism, I

Fig. 2 is an enlarged transverse vertical sectional view of the machine bed and throat plate of Fig. 1 and including a portion of the presser foot and of the feed dog illustrated in the elevated position of the feed dog,

.Fig. 3 represents a top plan view of the throat plate of my invention as applied to the bed of a sewing machine, and

Fig. 4 represents a perspective view of the metallic parts of the throat plate. i

Referring to Figs. 1, 2 and 3 of the drawing, the throat plate embodying my invention is illustrated as applied to plate which may be replaced in the event of wear or breakage. The throat plate is formed with a needle aperture and with slots through which the feed dog alternately raises and lowers into and out of engagement with the work. Bearing against the throat plate to hold the work fabrics firmly thereon is a presser device of which the most common form includes a spring biased presser foot. The presser device operates in opposition to the feed dog so that as the feed dog rises into engagement with the work, the presser foot is lifted slightly and the force exerted by the presser device is assumed by the feed dog. When the feed dog is lowered out of engagement with the work the presser device is lowered and the force is assumed by the throat plate. The alternate raising and lowering of the presser foot by the feed dog brings into play inertia effects which greatly magnify the static forces exerted by the presser foot, particularly at the high speed which modern sewing machines operate. The repeated impact of the presser foot on the throat plate constitutes, in effect, a hammering which gives rise to objectionable noise and to vibrations which in a conventional sewing machine are transmitted throughout the machine.

It is an object of this invention to provide an improved throat plate construction in which that portion of the work supporting surface which is in opposition to the presser foot is isolated from direct contact with the remainder of the sewing machine so that noise incident to the hammering action of the presser foot is reduced and the transmission of vibration incident thereto is minimized.

The various attempts which have been made in the past to cushion the throat plate of a sewing machine have not yielded completely satisfactory results for the reason that these prior attempts have all involved the use of a separate pad or gasket of cushioning material upon which the throat plate is supported. With the prior constructions, the degree of flaxibility required in order to effect a noticeable damping of noise and vibration was of such high order as to reduce the stability of the throat plate to an unfavorable level. It is pointed out that since the work is held against the throat plate when the stitches are set, any excessive movement of the throat plate will affect the character of the resulting stitch and, therefore, only a small degree of throat plate movement can be tolerated without a noticeable loss of quality and uniformity of stitching.

It is an object of this invention to provide a throat plate construction in which that portion which is in opposition to the presser foot is isolated from direct contact with the remainder of the sewing machine by a flexible a sewing machine of the type having a frame including a bed 11 defining a work supporting surface upon which the fabrics are placed during stitch formation. Supported by other parts of the sewing machine frame (not shown) above the bed is an endwise reciprocatory needle bar 12 carrying a needle 13 which cooperates with a loop taker 14 carried beneath the bed 11 in the concatenation of threads to form a stitch. Also carried above the bed is a presser bar 15 to whichis secured a presser foot 16 having a work engaging sole plate. The presser bar is biased downwardly by a conventional presser spring (not shown).

The bed 11 is cut away as at 17 beneath the needle and presser bars and the recess 17 is shouldered as at 18 to provide a shelf adapted snugly to receive a carrier plate 19 which is formed with countersunk apertures 20-20 to accommodate fiat head fastening screws 21-21 by which the carrier plate is secured to the bed preferably flush with the work supporting surface thereof. As illustrated in Fig. 3, in some sewing machines, the needle and presser bars are located at some distance inwardly from the outboard end of the bed in which case a slide cover plate 22 is provided to fill the recess from the outboard end of the bed to the carrier plate.

Referring to Fig. 4, the carrier plate is formed with a substantially rectangular opening or recess 23 which is preferably made larger than the presser foot sole plate and is disposed vertically beneath the presser foot when the carrier plate is secured to the bed. In the preferred embodiment illustrated in the drawings, the opening 23 at two opposite sides is defined by downwardly inclined converging surfaces 24, 24 preferably provided by lugs 25, 25 on the carrier plate which are struck down as illustrated in the drawings.

Disposed in the carrier plate opening 23 and spaced therefrom at all sides is a wear plate 26 formed with a needle aperture 27 and slots 28-28 designed to accommodate the teeth of a feed dog 29 of a conventional four motion work feeding mechanism carried in the bed. Of the feed mechanism, Figs. 1 and 2 of the drawing illustrate the feed dog 29 and a feed dog carrying bar 30 in lowered and raised position respectively, and Fig. l in addition illustrates a portion of a feed lift rock arm 31 and a link 32 between the rock arm and the feed bar by which the feed dog is raised and lowered.

In the preferred embodiment the edges of the wear plate on opposite sides thereof are beveled as at 33-33 and, as illustrated in Figs. 1 and 2, these beveled edges are formed substantially parallel to the inclined surfaces 2424 and in overlapping relation to the surfaces 24-24 when the wear plate is disposed inthe carrier plate opening substantially flush with the carrier plate. By flush it is meant that the top or work engaging surfaces of the wear and carrier plates are substantially co-planar.

interposed between the inclined surfaces 2424 of the carrier plate and the beveled edges 3333 of the wear plate is flexible rubberlike cushioning material 34 which is the sole support for the wear plate with respect to the carrier plate. The cushioning material may be of natural or synthetic rubber and it is preferably bonded, i.e., glued, vulcanized etc. to both the wear and carrier plate surfaces thereby amalgamating the wear and carrier plates into a single throat plate unit.

The inclined converging surfaces 2424 of the carrier plate and similarly the beveled edges 3333 of the wear plate are preferably formed at an angle of 45 with the work supporting surfaces of these members as indicated as x in Fig. 2.

Since the repetitive forces exerted on the wear plate by the presser foot occur generally downwardly, the cushioning material being inclined with respect to the direction of application of these forces, will be stressed partly in shear and partly in compression. Although the distribution of forces during actual machine operation would appear to be complex, it has been found that with this arrangement of cushioning material, vibration will be effectively isolated and noise incident to hammering of the presser foot materially reduced without appreciable sacrifice of the stability of the wear plate necessary for high quality stitch formation.

The inclined arrangement of the cushioning material and the manner in which the parts are formed in this invention to accommodate the cushions, moreover, provides a composite throat plate unit which is not appreciably larger in dimension than the usual one-piece throat plates commonly used in the art. An advantage of this invention, therefore, is that my improved throat plate may be used readily on existing machines with little or no alteration of the machine being required.

Having thus described the nature of the invention, what I claim herein is:

1. A throat plate for a sewing machine of the type having a bed plate defining a work supporting surface and a presser member having a work engaging sole plate supported in opposition to said work supporting surface, said throat plate comprising, a carrier plate formed with an opening bounded on two opposite sides by inclined converging surfaces, means for securing said carrier plate to said bed plate substantially flush with said work supporting surface and with said opening disposed opposite to the sole plate of said presser member, a wear plate disposed in said carrier plate opening substantially flush with said carrier plate, the edges of said wear plate at opposite sides thereof being beveled and disposed overlapping and substantially parallel to said inclined carrier plate surfaces, and flexible rubber-like cushioning material interposed between and bonded to the beveled sides of said wear plate and the inclined surfaces of said carrier plate.

2. A throat plate for a sewing machine of the type having a bed plate defining a work supporting surface and a presser member having a work engaging sole plate supported in opposition to said work supporting surface, said throat plate comprising, a carrier plate formed with a substantially rectangular opening bounded on two opposite sides by lugs stuck out at a downward inclination from said carrier plate, means for securing said carrier plate to said bed plate substantially flush with said work supporting surface and with said opening disposed opposite to the sole plate of said presser member, a wear plate disposed in said carrier plate opening substantially flush with said carrier plate the edges of said wear plate on two opposite sides thereof being beveled and substantially parallel to the downwardly inclined lugs stuck out from said carrier plate, and flexible rubber-like cushioning material bonded in place between the beveled edges of said wear plate and the carrier plate lugs and providing the only support for said wear plate.

References Cited in the file of this patent UNITED STATES PATENTS 363,655 Littlejohn May 24, 1887 1,145,175 Weis July 6, 1915 1,360,357 Bauer Nov. 30, 1920 2,118,550 Aubarede May 24, 1938 2,644,413 Sauer July 7, 1953 FOREIGN PATENTS 98,496 Austria Nov. 10, 1924 553,793 Great Britain June 7, 1943 

